The invention relates to a device enabling an individual to self-monitor his breathing in order to assist in the control of a radiotherapy unit for the treatment of tumours or an imaging unit.
The tumours are ones located in the region of the thoracic cage (lungs, breast, etc.) or tumours, the position of which varies as a function of expansion of the thorax (liver, etc.)
One of the major difficulties in radiotherapy is that of irradiating the tumour with rays, especially X-rays, while limiting as far as possible irradiation of healthy tissues located in the immediate vicinity of the tumour. Also, in the treatment of a tumour, the patient is conventionally invited to inflate his lungs as far as possible in order to achieve a state in which there is a minimum amount of tissue per unit of surface area and also to achieve optimally uniform ray penetration of the infected tissues to be treated. Once the practitioner has judged the inflation to be satisfactory, the patient is invited to hold his breath and to maintain an apnea during the irradiation process.
Lung ventilation capacity, which results in the capacity to inflate or to contract the lungs, varies from person to person. Moreover, different individuals experience stress differently, so some people have difficulty in controlling their breathing and therefore in stabilising the organ to be treated.
Furthermore, various devices have been developed, on the one hand, for helping the practitioner to control a radiotherapy unit and, on the other hand, for helping the patient to achieve adequate levels of inflation or contraction of the lungs for the treatment that he has to undergo.
FR-2.823.679, for example, describes a device for controlling a radiotherapy unit comprising means for measuring the expansion of the thorax of a patient and a control unit capable of comparing, in a first stage, the measured values of the expansion of the thorax with stored values of the expansion of the patient's thorax during rest and for triggering, in a second stage, the irradiation process once the measured values reach pre-established thorax expansion limit values and correspond to an inflation of the lungs capable of qualitative treatment. This device is also provided with display means allowing the patient and the practitioner to visualise the development over time of the expansion of the thorax and the triggering values to be reached before radiotherapy may be undergone.
Although the characteristics of this device are established, especially owing to its widespread use in hospital centres, it does not allow the most stressed patients to reach the desired triggering levels. Indeed, it has been found that a stressed patient who sees from a display device that his level of lung expansion is far from the limit to be reached will tend to force his breathing. This will, at best, enable him to reach this triggering level of lung expansion, but will not allow him to hold his breath for a sufficiently long time and in a sufficiently stable manner—a necessary condition for safe irradiation.
The device described in WO 99/43260 is a device helping to trigger the irradiation process by analysing a specific number of parameters that reflect the state of a patient's breathing—air flow rate, pressure, estimated lung volume, and CO2 concentration—and are fed to the input of a control unit capable of triggering, under the supervision of the practitioner, the irradiation process once the compiling of these parameters reveals nominal lung expansion conditions for the patient in question.
This device helps the practitioner to choose the right moment for triggering the irradiation process, but does not allow the patient either to visualise or to monitor the moment of irradiation.